1. Field of the Invention
This invention relates to an air filter for an engine and, more particularly, relates to an air filter for a small engine suitable for use in an automobile or a motor-bicycle.
2. Description of the Prior Art
A conventional air filter for an engine has an air suction box provided in an air suction passage for communicating an inside of a combustion chamber of the engine with atmosphere. The air suction box is divided by a filter element into an upstream side and a downstream side in an air current direction. Accordingly, an entire air to be suctioned into the combustion chamber is passed through the air suction box. The air suctioned into the air suction box is included with relatively large foreign matters such as soot and sand dust, and fine foreign maters such as floating powder dust. It is difficult to remove such dust effectively by a so-called air filter using sponges or paper filters. Specifically, if the mesh of the filter is set small in order to remove effectively the fine dust, the filter is choked easily and if the mesh of the filter is set large, the fine dust cannot be removed.
In order to remove a relatively large dust, it has been proposed to use two kinds of filters and arranged in series in the air suction passage. One kind of the filter is the above mentioned filtration type filter. The other kind of filter is a wet type filter such as an oil pass type filter or an enertia type filter such as a cyclone.
However, if two or more kinds of filters are provided in the air suction passage, a large space is required and such filters cannot be used for the small automobile or the motor-bicycle having no large space for installing the engine.
An object of the present invention is to solve the above problems.
Another object of the present invention is to provide an air filter for an engine comprising an air suction box, and a filter element for dividing the air suction box into an upstream side of an air current and a downstream side of the air current, the upstream side of the suction box being communicated with atmosphere through a suction cylinder of relatively large diameter and an air exhaust cylinder of relatively small diameter, both cylinders being arranged coaxially with each other through a small air space.
Further object of the present invention is to provide the air filter for the engine, wherein the air suction box is made of a synthetic resin and composed of one half portion and the other half portion connected to each other through the filter element, the air suction cylinder is provided in the one half portion, and the air exhaust cylinder is provided in the other half portion, the insides of the both half portions being defined by the filter element.
Still further object of the present invention is to provide the air filter for the engine, wherein the air suction cylinder is in a form of funnel having a large diameter at the atmosphere side thereof and a small diameter at the air exhaust side thereof, and the air exhaust cylinder is in a form of funnel having a large diameter at the air suction side thereof and a small diameter at the atmosphere side thereof.
These and other aspects and objects of the present invention will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following description, while indicating preferred embodiments of the present invention, is given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.